This invention relates to rotary valves and, in particular, to seals for bidirectional rotary valves.
Valve seal design is dictated by the use to which the valve will be put. Parameters controlling the choice of rotary valve seal include: the mean fluid pressure and pressure range; the mean fluid flow rate and flow rate range; the torque requirements for actuating the valve; the maximum permissible leakage rate; and whether the fluid flow will be unidirectional or bidirectional. The prior art is replete with valve seals designed to meet different ranges and combinations of these parameters.
One particular type of rotary valve seal is a resilient sealing element mounted in the valve body by a retaining ring. The sealing element typically has a straight outer periphery mounted between the retaining ring and the valve body and a curved portion which contacts the valve member. Examples of this type of seal are shown by U.S. Pat. No. 4,796,857 to Hayes et al.; U.S. Pat. No. 4,491,298 to Beauchamp et al.; U.S. Pat. No. 4,241,895 to Sternenberg et al.; and U.S. Pat. No. 4,231,546 to Eggleston et al. The disclosures of these patents are incorporated herein by reference.